1. Field Of The Invention
The present invention relates to user-programmable antifuse devices. More particularly, the present invention relates to methods for programming antifuse devices.
2. The Prior Art
All antifuse processes produce antifuses with programming voltages that are distributed over a range of voltages (e.g. 8-13 volts). Typical programming algorithms apply a programming voltage (V.sub.pp) that is greater than the anticipated maximum programming voltage in order to assure the desired antifuse is programmed (e.g. V.sub.pp =13.5 volts).
Utilization of this typical prior art antifuse programming regime is likely to have a negative impact on antifuse programming yield. The reason is that antifuses which are intended to be left unprogrammed may become overstressed and be thereby weakened or inadvertently programmed.
It is an object of the present invention to reduce the probability of inadvertent programming of any antifuse other than the intended one.
It is a further object of the present invention to reduce leakage current through unprogrammed fuses during the programming cycle so that leakage load on the programming circuit is reduced and circuit nodes that are floating during programming will drift less in voltage and more slowly in time.
Yet another object of the present invention is to allow the use of antifuse elements with a wider programming voltage and leakage characteristic than would be possible without the present invention.
A further object of the invention is to reduce, during the programming period, the stress introduced on antifuses which will not be programmed.